1. Field of the Invention
The present invention relates to an apparatus and method for inspecting substrates such as semiconductor wafers and liquid crystal panels, more specifically to a substrate inspection apparatus for automatically measuring stress and/or a composition of thin films provided on a surface of a substrate or various patterned microfabricated parts, and further, can provide thickness and the index of refraction of the thin film at the time of measurement.
2. Description of the Prior Art
In a semiconductor manufacturing process, quality control of a substrate such as a semiconductor wafer is extremely important. Particularly, acquiring physical information such as thickness, index of refraction, stress and composition of the thin film prepared on the surface of the semiconductor wafer and the like and controlling the same so as to be in an appropriate state, is necessary to maintain a stable performance of the semiconductor device and the electronic circuit fabricated on the semiconductor wafer.
A CMOS circuit is used to achieve a high performance large-scale integrated circuit (LSI) in a sub-100 nm region in the semiconductor device, and high performance, high-speed of CMOS circuit are essential factors in manufacturing semiconductors. In order to have the CMOS circuit of high performance and high-speed, a method of shortening the gate length and a method of increasing the carrier speed are proposed, but if the circuit is miniaturized to shorten the gate length, a short channel effect occurs and thus miniaturization of the circuit has limitations.
Recently, for a technique of achieving high-performance without greatly shortening the gate length, a technique of manufacturing semiconductor devices using strained silicon with carrier mobility far greater than the normal silicon has been considered. This is a technique of improving carrier mobility by forming a silicon layer on a SiGe layer, where the lattice constant is larger than that of silicon, and applying tensile strain on the silicon layer (thin film) to modulate the silicon band structure. Further, in order to improve the performance of the MOSFET while suppressing the short channel effect, thin filming of the gate oxide film is performed but the procedure has limitations, and thus the strained silicon technique is again given attention as a means for providing a MOSFET of high performance without involving thin filming of the oxide film.
In recent semiconductor wafer manufacturing, it is necessary to perform an examination associated with thickness and stress measurement of the thin film to improve quality control/productivity. A Raman spectroscopic technique is conventionally known for a stress measurement of semiconductor materials such as silicon. The stress measurement using the Raman spectroscopic technique is such in which the stress at the measurement point is estimated from a change of peak positions of the Raman spectrum by using the fact that the Raman spectrum shifts when stress acts on the single crystal silicon and the like.
In Japanese Laid-Open Patent Publication No. 8-5471, the structure of a stress measurement method and a stress measurement device for performing stress measurement using Raman spectroscopy in a semiconductor device manufacturing process is disclosed. Inspection of each part relating to stress in the manufacturing process is performed by means of the stress measurement device disclosed in Japanese Laid-Open Patent Publication No. 8-5471 so as to improve quality control and productivity.
However, since the stress measurement apparatus disclosed in Japanese Laid-Open Patent Publication No. 8-5471 cannot sequentially and automatically measure the surface of a plurality of wafers, the quality evaluation cannot be sufficiently performed on all the manufactured semiconductor wafers or the semiconductor devices, and an accurate process control in the manufacturing process of the wafer becomes difficult. Further, in obtaining film thickness in addition to stress for each microfabricated part, it is important to find a correlation between stress and film thickness in manufacturing the semiconductor wafer, but stress and film thickness cannot be measured for the wafer.
In addition, it is supposed that when embedding a thick oxide film such as a trench configuration in the semiconductor device, a particularly significant stress concentration is likely to occur near the microfabricated part. Thus, if the thick oxide film is formed at the microfabricated part in the sub-100 nm region, stress produced at the interface of the thin films becomes great and heat or stress is generated even when stress similar to when forming a relatively thin oxide film is acted, which may become the cause of defects such as thermal migration or stress migration. Therefore, finding the relationship between stress and film thickness at the same microscopic region becomes important in quality control of the wafer.
In developing future semiconductor wafers, in particular, the strained silicon technique is likely to be introduced and thus the strained silicon tends to be formed in the semiconductor wafer. Therefore, measuring various physical quantities such as internal stress and film thickness of the strained silicon, and further, composition of SiGe layer serving as a base layer, and analyzing the correlation between film thickness and stress are becoming increasingly important, and adjusting the manufacturing process so as to control the conditions of stress and film thickness to be optimum and manufacturing the semiconductor wafer so as to manufacture an integrated circuit of higher performance are extremely important. In manufacturing the semiconductor wafer adopting the strained silicon technique, the inspection process of all the manufactured wafers is considered necessary, but a substrate inspection apparatus for simply and easily performing stress measurement and film thickness measurement does not exist.
In a laser anneal equipment disclosed in Japanese Laid-Open Patent Publication No. 9-213652, a Raman spectroscopic photometer and an ellipsometer are mounted to allow measurement of structure and index of refraction of the crystalline silicon film immediately after laser anneal, but since the measurement points of the Raman/ellipsometer optical systems differ each other, various physical information at a specific microscopic region cannot be obtained all at once. Further, an equipment of Japanese Laid-Open Patent Publication No. 9-213652 is included in the equipment of the manufacturing process and thus is difficult to be applied for use as an inspection apparatus.